Electric field guidance system for automated vehicles

Abstract

An automated vehicle guidance system (100) includes automated self-propelled vehicles (102) selectively traveling a guidepath (114) comprising a plurality of interconnected guidelines (110, 116, 118). The guidepath (114) comprises an electric field wire system comprising a series of wire segments buried under a floor surface (112), and excited by an alternating current (AC) voltage source (210) referenced to earth ground. Voltage probes (222, 224) sense the electric field emanating from the guidepath segments and generate an intelligence signal for appropriately steering the vehicle (102) along the guidepath (114).

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. An automated vehicle guidance system having one or more self-propelled vehicles adapted to follow a predetermined guidepath having path signal generating means for generating signals on said guidepath, and wherein each of said vehicles includes guidepath sensing means for sensing the position of the guidepath with respect to the vehicle, signal generating means connected to said sensing means for generating an intelligence signal representative of the position of the vehicle with respect to the guidepath, and control means for steering the vehicle in response to the intelligence signal generated by the signal generating means so as to maintain a given position of the vehicle with respect to the guidepath as the vehicle moves therealong, the improvement wherein: the path signal generating means comprises means for exciting the guidepath with an AC voltage signal referenced to an earth ground;   the guidepath sensing means comprises electric field sensing means for sensing the strength of the electric field resulting from the voltage signal; and   the signal generating means is connected to the electric field sensing means and is responsive to the sensed strength of the electric field for generating the intelligence signal.   
     
     
       2. An automated vehicle guidance system in accordance with claim 1 wherein the path signal generating means comprises an AC voltage source having one terminal connected to an earth ground and another terminal connected to a conductor on the guidepath. 
     
     
       3. An automated vehicle guidance system in accordance with claim 2 wherein the conductor. and the AC voltage source form a closed-loop electrical path only through capacitive coupling to the earth ground. 
     
     
       4. An automated vehicle guidance system in accordance with claim 1 wherein the guidepath sensing means comprises a pair of voltage probes mounted on the vehicle so that the relative strength of the electric field sensed by one of the probes is substantially different from the relative strength of the electric field sensed by the other probe only when the vehicle deviates from the given position with respect to the guidepath. 
     
     
       5. An automated vehicle guidance system in accordance with claim 4 wherein the guidepath sensing means further comprises means for providing capacitance between the voltage probes and the earth ground. 
     
     
       6. An automated vehicle guidance system in accordance with claim 5 wherein the vehicle includes a base having a relatively large conductive surface, and the surface provides the capacitance. 
     
     
       7. An automated vehicle guidance system in accordance with claim 4 wherein the signal generating means comprises means connected to the voltage probes for generating the intelligence signal as representative of the difference between signal strengths of the electric field as sensed by the voltage probes. 
     
     
       8. An automated vehicle guidance system in accordance with claim 7 wherein the signal generating means further comprises means to provide synchronous detection and automatic gain control of signals generated by the voltage probe and the steering error signal.